U.S. patent application number 17/370193 was filed with the patent office on 2022-03-03 for polyurethane golf ball.
The applicant listed for this patent is VOLVIK INC.. Invention is credited to Kyung Ahn MOON, Seung Geun PARK, Geon SIM, Chul Ho SONG.
Application Number | 20220062713 17/370193 |
Document ID | / |
Family ID | 1000005896764 |
Filed Date | 2022-03-03 |
United States Patent
Application |
20220062713 |
Kind Code |
A1 |
SONG; Chul Ho ; et
al. |
March 3, 2022 |
POLYURETHANE GOLF BALL
Abstract
A golf ball according to an embodiment of the present disclosure
is covered with an injection-molded crosslinked polyurethane. The
golf ball may have excellent scuff resistance and light resistance
of a cover as well as excellent driving distance and spin by using
a cover composition containing crosslinked polyurethane obtained by
adding a crosslinking agent to thermoplastic polyurethane (TPU). A
polyurethane cover composition according to an embodiment can make
it possible to prepare a crosslinked polyurethane cover by
injection molding without the burden of facility investment
cost.
Inventors: |
SONG; Chul Ho; (Gyeonggi-do,
KR) ; PARK; Seung Geun; (Chungcheongbuk-do, KR)
; SIM; Geon; (Seoul, KR) ; MOON; Kyung Ahn;
(Seoul, KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
VOLVIK INC. |
Chungcheongbuk-Do |
|
KR |
|
|
Family ID: |
1000005896764 |
Appl. No.: |
17/370193 |
Filed: |
July 8, 2021 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C08G 18/10 20130101;
C08L 75/08 20130101; C08G 18/758 20130101; A63B 37/005 20130101;
C08K 5/29 20130101; C08G 18/7621 20130101; C08G 18/755 20130101;
C08G 18/42 20130101; C08K 5/0025 20130101; C08G 18/48 20130101;
C08L 75/06 20130101; C08G 18/3212 20130101; C08G 18/3206 20130101;
A63B 37/00373 20200801; C08F 136/06 20130101; A63B 37/0039
20130101; C08G 18/73 20130101; C08L 23/0869 20130101 |
International
Class: |
A63B 37/00 20060101
A63B037/00; C08L 75/06 20060101 C08L075/06; C08L 75/08 20060101
C08L075/08; C08F 136/06 20060101 C08F136/06; C08L 23/08 20060101
C08L023/08; C08G 18/10 20060101 C08G018/10; C08G 18/48 20060101
C08G018/48; C08G 18/42 20060101 C08G018/42; C08G 18/32 20060101
C08G018/32; C08G 18/75 20060101 C08G018/75; C08G 18/73 20060101
C08G018/73; C08G 18/76 20060101 C08G018/76; C08K 5/00 20060101
C08K005/00; C08K 5/29 20060101 C08K005/29 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 26, 2020 |
KR |
10-2020-0107516 |
Jan 7, 2021 |
KR |
10-2021-0001827 |
Claims
1. A golf ball comprising: a core comprising a polybutadiene
rubber; an inner cover comprising an ionomer resin; and an outer
cover comprising crosslinked polyurethane formed by reaction of
thermoplastic polyurethane and a crosslinking agent, wherein the
crosslinking agent comprises an isocyanate crosslinking agent and a
compound represented by Chemical Formula 1: ##STR00007## wherein
each of R1, R2 and R3 is independently H, OH or a C.sub.1-C.sub.10
alkoxy group, with one of R1, R2 and R3 being OH, and each of x and
y is independently an integer of 1-2.
2. The golf ball according to claim 1, wherein the thermoplastic
polyurethane is obtained by reacting at least one long-chain polyol
selected from a group consisting of aliphatic polyether polyol and
polyester polyol.
3. The golf ball according to claim 1, wherein the thermoplastic
polyurethane is obtained by reacting at least one diisocyanate
selected from a group consisting of HDI (hexamethylene
diisocyanate), IPDI (isophorone diisocyanate), H.sub.12MDI
(4,4'-dicyclohexylmethane diisocyanate) and 1,4-H.sub.6XDI
(1,4-hydrogenated xylene diisocyanate).
4. The golf ball according to claim 1, wherein the thermoplastic
polyurethane comprises at least one chain extender selected from
ethylene glycol, diethylene glycol, 1,3-propanediol,
1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol,
bishydroxymethylcyclohexane and cyclohexane-1,4-diol.
5. The golf ball according to claim 1, wherein the crosslinked
polyurethane has a Shore D hardness of 30-60.
6. The golf ball according to claim 1, wherein the isocyanate
crosslinking agent is at least one compound selected from MDI
(methylene diphenyl diisocyanate), polymeric MDI, TDI (toluene
diisocyanate), HDI (hexamethylene diisocyanate), IPDI (isophorone
diisocyanate), H.sub.12MDI (dicyclohexylmethane diisocyanate), MDI
isocyanurate (t-MDI), TDI isocyanurate (t-TDI), HDI isocyanurate
(t-HDI) and IPDI isocyanurate (t-IPDI).
7. The golf ball according to claim 1, wherein the crosslinked
polyurethane is formed as 100 parts by weight of the thermoplastic
polyurethane reacts with 0.1-20 parts by weight of the crosslinking
agent.
8. The golf ball according to claim 1, wherein the crosslinked
polyurethane has a degree of crosslinking of 10-90.
9. The golf ball according to claim 1, wherein the crosslinked
polyurethane experiences color change (.DELTA.E) of 8 or less after
exposure to irradiance of 1 SUN (1,000 W/m.sup.2) for 120
hours.
10. The golf ball according to claim 1, wherein the ionomer resin
is a copolymer of ethylene and unsaturated carboxylic acid with a
part of the unsaturated carboxylic acid being neutralized with a
monovalent or divalent metal ion.
Description
CROSS REFERENCE TO RELATED APPLICATIONS AND CLAIM OF PRIORITY
[0001] This application claims the benefit of Korean Patent
Application Nos. 10-2020-0107516 filed on Aug. 26, 2020 and
10-2021-0001827 filed on Jan. 7, 2021, in the Korean Intellectual
Property Office, the disclosures of which are incorporated herein
by reference in its entirety.
BACKGROUND
1. Technical Field
[0002] The present disclosure relates to a golf ball covered with
an injection-molded crosslinked polyurethane cover with excellent
scuff resistance and light resistance, more particularly to a
polyurethane golf ball with excellent scuff resistance and light
resistance of a cover as well as excellent driving distance and
spin by using a cover composition containing crosslinked
polyurethane obtained by adding a crosslinking agent to
thermoplastic polyurethane (TPU).
2. Background Art
[0003] At present, the cover of premium-grade golf balls has mainly
a dual cover structure consisting of an outer cover and an inner
cover.
[0004] As the inner cover, a SURLYN.RTM.-based ionomer resin is
typically used. The ionomer resin, which is strong and rigid,
protects the inner core when the golf ball is hit and greatly
increases driving distance by delivering force wholly to the
center.
[0005] As the outer cover, a soft and tough polyurethane resin is
typically used.
[0006] A three-piece golf ball is obtained when the dual cover is
combined with a single core, and a four-piece golf ball is obtained
when it is combined with a dual core.
[0007] The dual cover structure of the golf ball is employed to
satisfy various properties required for the golf ball, such as
driving distance, spin, hitting characteristics, rebound
resilience, etc.
[0008] As a material of the outer cover, polyurethane is commonly
used to allow easier control over the amount of spin when the golf
ball is hit with an iron. The polyurethane used for the golf ball
cover is largely classified into thermosetting polyurethane and
thermoplastic polyurethane (TPU).
[0009] For preparation of thermosetting polyurethane into a golf
ball cover, a casting molding method of adding solutions of a
prepolymer and a curing agent together is commonly used. However,
the casting method has the problems that the control of reaction
rate is difficult because the curing reaction is carried out after
the solutions of the prepolymer and the curing agent are added
separately and then mixed, the productivity is not good because
time is necessary for the curing, and high initial investment cost
is required to establish a long casting line for a continuous
process.
[0010] Thermoplastic polyurethane (TPU) is highly advantageous in
that injection molding is possible because it has thermoplasticity
due to a linear molecular structure. Injection molding using the
thermoplastic polyurethane material is very desirable method for
molding the golf ball cover owing to high productivity due to very
short molding time as compared to the casting of thermosetting
polyurethane.
[0011] U.S. Pat. Nos. 3,395,109, 4,248,432, 4,442,282, etc.
previously proposed a golf ball using thermoplastic polyurethane.
However, the golf ball cover was not satisfactory in terms of
hitting characteristics, spin control, scuff resistance, light
resistance, etc.
[0012] U.S. Pat. No. 6,258,310 disclosed a technology of modifying
thermoplastic polyurethane (TPU) using an extruder, wherein an MDI
(methylene diphenyl diisocyanate)-terminated prepolymer is added to
TPU to introduce crosslinkage. In addition, US Patent Publication
No. 2009-0230587 disclosed a method for preparing partially
crosslinked thermoplastic polyurethane by mixing a monomeric MDI
and an aromatic diamine in thermoplastic polyurethane (TPU) and a
method for manufacturing a golf ball cover by injection-molding the
same.
[0013] Since these US patents use an aromatic isocyanate and an
aromatic amine, the yellowing of the prepared PU cover upon
exposure to light could not be avoided.
[0014] Korean Patent Publication No. 2006-0115591 disclosed a golf
ball with rebound resilience and scuff resistance improved by
introducing a crosslinking agent to an isocyanate master batch
(Crossnate EM30, MDI content=30%) in order to crosslink PTMG-MDI-BD
thermoplastic polyurethane. However, yellowing due to long-term
exposure to light could not be avoided because the aromatic
isocyanate MDI is a basic unit.
[0015] Korean Patent Registration No. 1047087 disclosed a golf ball
with excellent scuff resistance by crosslinking thermoplastic
polyurethane using an unsaturated diol, i.e., trimethylolpropane
monoallyl ether (TMPME) having a double bond, as a chain extender
and using a free radical reaction initiator. However, it is
difficult to control crosslinkage once the reaction is initiated
and the prepared resin can be hardly used for injection molding
since its property is the same as that of the thermosetting
resin.
[0016] Korean Patent Registration No. 1518108 pointed out that the
use of thermoplastic polyurethane leads to weak scuff resistance
upon hitting by an iron although excellent rebound resilience and
spin performance can be achieved and, in order to solve this
problem, disclosed that physical properties were improved by
replacing some of the polyol reacted with an aromatic isocyanate
for synthesis of polyurethane with a hyperbranched polyol.
[0017] Korean Patent Registration No. 1437411 disclosed that a golf
ball cover composition with improved scuff resistance was obtained
by replacing some of the polyol for preparation of polyurethane
with a hyperbranched polyol and using an acrylate having a hydroxyl
group.
[0018] Although these Korean patents attempted to improve physical
properties by introducing partial crosslinkage by mixing some of
the polyol used for preparation of a thermoplastic polyurethane
resin with an acrylate having a hydroxyl group or a double bond,
the yellowing phenomenon occurring upon long-term exposure to light
due to weak light resistance could not be avoided because an
aromatic isocyanate was used. Therefore, they are not suitable for
a golf ball including a colored (pigmented) outer cover.
SUMMARY
[0019] The inventors of the present disclosure have made efforts to
develop a golf ball including a cover with excellent scuff
resistance and light resistance. As a result, they have identified
that scuff resistance, light resistance, etc. can be improved by
using partially crosslinked polyurethane obtained by reacting
thermoplastic polyurethane with a specific crosslinking agent in an
outer cover, and have completed the present disclosure.
[0020] The present disclosure is directed to providing a golf ball
including:
[0021] a core containing a polybutadiene rubber;
[0022] an inner cover containing an ionomer resin; and
[0023] an outer cover containing crosslinked polyurethane formed by
reaction of thermoplastic polyurethane and a crosslinking
agent,
[0024] wherein the crosslinking agent includes an isocyanate
crosslinking agent and a compound represented by Chemical Formula
1:
##STR00001##
[0025] wherein each of R1, R2 and R3 is independently H, OH or a
C.sub.1-C.sub.10 alkoxy group, with one of R1, R2 and R3 being OH,
and
[0026] each of x and y is independently an integer of 1-2.
[0027] The thermoplastic polyurethane may be obtained by reacting
at least one long-chain polyol selected from a group consisting of
aliphatic polyether polyol and polyester polyol.
[0028] The thermoplastic polyurethane may be obtained by reacting
at least one diisocyanate selected from a group consisting of HDI
(hexamethylene diisocyanate), IPDI (isophorone diisocyanate),
H.sub.12MDI (4,4'-dicyclohexylmethane diisocyanate) and
1,4-H.sub.6XDI (1,4-hydrogenated xylene diisocyanate).
[0029] The thermoplastic polyurethane may include at least one
chain extender selected from ethylene glycol, diethylene glycol,
1,3-propanediol, 1.3-butanediol, 1,4-butanediol, 1,5-pentanediol,
1,6-hexanediol, bishydroxymethylcyclohexane and
cyclohexane-1,4-diol.
[0030] The crosslinked polyurethane may have a Shore D hardness of
30-60. The isocyanate crosslinking agent may be at least one
compound selected from HDI (hexamethylene diisocyanate), IPDI
(isophorone diisocyanate), H.sub.12MDI (dicyclohexylmethane
diisocyanate), HDI isocyanurate (t-HDI) and IPDI isocyanurate
(t-IPDI).
[0031] The crosslinked polyurethane may be formed as 100 parts by
weight of the thermoplastic polyurethane reacts with 0.1-20 parts
by weight of the crosslinking agent.
[0032] The crosslinked polyurethane may have a degree of
crosslinking of 10-90.
[0033] The crosslinked polyurethane may experience color change
(.DELTA.E) of 8 or less after exposure to irradiance of 1 SUN
(1,000 W/m.sup.2) for 120 hours.
[0034] The ionomer resin may be a copolymer of ethylene and
unsaturated carboxylic acid with a part of the unsaturated
carboxylic acid being neutralized with a monovalent or divalent
metal ion.
[0035] The polyurethane cover composition according to the present
disclosure can be prepared into a crosslinked polyurethane cover by
injection molding without the burden of facility investment cost
since no additional casting molding facility is necessary.
[0036] In addition, when an outer cover of a golf ball is prepared
using the polyurethane cover composition of the present disclosure,
the driving distance, spin control performance, scuff resistance
and light resistance of the golf ball can be improved greatly.
BRIEF DESCRIPTION OF DRAWINGS
[0037] FIG. 1 shows the FT-IR spectrum of a crosslinking agent
prepared in Preparation Example 1.
[0038] FIG. 2 shows the FT-IR spectrum of vanillin
(4-hydroxy-3-methoxybenzaldehyde).
[0039] FIG. 3 shows the FT-IR spectrum of Jeffamine.RTM. T-403.
[0040] FIG. 4 shows the .sup.1H NMR spectrum of a crosslinking
agent prepared in Preparation Example 1.
[0041] FIG. 5 shows the .sup.1H NMR spectrum of vanillin
(4-hydroxy-3-methoxybenzaldehyde).
[0042] FIG. 6 shows the .sup.1H NMR spectrum of Jeffamine.RTM.
T-403.
DETAILED DESCRIPTION
[0043] Hereinafter, the present disclosure is described in detail.
The terms used in the specification and claims should not be
understood to be limited by the common or dictionary meanings, but
should be understood within the context of the present disclosure
based on the principle that the concept of the terms can be
adequately defined by an inventor to best describe his/her own
invention.
[0044] The present disclosure provides a golf ball including:
[0045] a core containing a polybutadiene rubber;
[0046] an inner cover containing an ionomer resin, which is a
copolymer of ethylene and unsaturated carboxylic acid with a part
of the unsaturated carboxylic acid being neutralized with a
monovalent or divalent metal ion; and
[0047] an outer cover containing crosslinked polyurethane formed by
reaction of thermoplastic polyurethane and a crosslinking
agent,
[0048] The crosslinked polyurethane may be obtained by adding a
crosslinking agent to non-yellowing-type thermoplastic polyurethane
(TPU) and then performing extrusion reaction.
[0049] Whereas a casting method is commonly used to prepare an
outer cover of a golf ball using urethane, the present disclosure
provides crosslinked polyurethane which allows the preparation of a
urethane cover of a golf ball by injection molding.
[0050] The thermoplastic polyurethane is not particularly limited
as long as it is one commonly used for preparation of a golf ball.
More specifically, at least one compound selected from aliphatic
polyether polyol and polyester polyol as a high-molecular-weight
long-chain polyol having excellent light resistance and
constituting the soft segment of thermoplastic polyurethane may be
used. More specifically, the aliphatic polyester polyol may be, for
example, polyethylene adipate diol, polypropylene adipate diol or
polybutylene adipate diol, although not being limited thereto. As
the polyether diol, PTMG (polytetramethylene glycol) with a
molecular weight of 800-3000 may be used, although not being
limited thereto.
[0051] In the thermoplastic polyurethane, as the diisocyanate which
forms urethane bonding by reacting with the high-molecular-weight
long-chain diol, an aliphatic diisocyanate or an alicyclic
diisocyanate with excellent light resistance may be used either
alone or in combination. The diisocyanate may be selected from a
group consisting of HDI (hexamethylene diisocyanate), IPDI
(isophorone diisocyanate), H.sub.12MDI (4,4'-dicyclohexylmethane
diisocyanate) and 1,4-H.sub.6XDI (trans-1,4-hydrogenated xylylene
diisocyanate), although not being limited thereto.
[0052] In addition, a low-molecular-weight diol such as an aromatic
diol or an aliphatic diol may be used as a chain extender
constituting the thermoplastic polyurethane. More specifically, an
aliphatic diol with excellent light resistance is preferred. More
specifically, an aliphatic diol such as ethylene glycol, diethylene
glycol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol,
1,5-pentanediol, 1,6-hexanediol, etc. may be used, although not
being limited thereto. And, the alicyclic diol may be, for example,
bishydroxymethylcyclohexane, cyclohexane-1,4-diol, etc., although
not being limited thereto.
[0053] The thermoplastic polyurethane may have a Shore D hardness
of specifically 30-60, more specifically 35-55. If the Shore D
hardness is below 30, the cover may be damaged easily. And, if it
exceeds 60, spin performance may be unsatisfactory.
[0054] As a crosslinking agent compound for crosslinking the
thermoplastic polyurethane, an isocyanate-based crosslinking agent
such as polyisocyanate, polyisocyanurate, etc. may be used.
[0055] The isocyanate crosslinking agent may be at least one
non-yellowing type crosslinking agent selected from HDI
(hexamethylene diisocyanate), IPDI (isophorone diisocyanate),
H.sub.12MDI (dicyclohexylmethane diisocyanate), HDI isocyanurate
(t-HDI) and IPDI isocyanurate (t-IPDI).
[0056] In addition, MDI (methylene diphenyl diisocyanate), TDI
(toluene diisocyanate) or t-MDI (MDI trimer) having an
intramolecular benzene structure may also be used as the isocyanate
crosslinking agent. The crosslinking agent having an intramolecular
benzene structure may be added in an amount of 0.1-10 parts by
weight based on 100 parts by weight of the non-yellowing type
crosslinking agent, so that light resistance is not affected
significantly.
[0057] As the crosslinking agent compound, polyisocyanurate such as
MDI isocyanurate (t-MDI), TDI isocyanurate (t-TDI), HDI
isocyanurate (t-HDI), IPDI isocyanurate (t-IPDI), etc. may be used.
More specifically, non-yellowing type HDI isocyanurate (t-HDI) or
IPDI isocyanurate (t-IPDI) with excellent light resistance may be
used. When MDI isocyanurate (t-MDI) or TDI isocyanurate (t-TDI) is
used, it may be added in an amount of 0.1-10 parts by weight based
on 100 parts by weight of the non-yellowing type polyisocyanurate,
so that light resistance is not affected significantly.
[0058] The polyisocyanurate may be advantageous to form a
crosslinked network structure since it forms a hexagonal ring with
three isocyanate (NCO) functional groups arranged with an angle of
120.degree..
[0059] The polyisocyanate crosslinking agent compound may form an
allophanate bond by reacting with the urethane bond of TPU in an
extruder. The formed network structure is thermally very
stable.
[0060] In addition, the crosslinking agent includes a crosslinking
agent compound represented by Chemical Formula 1.
##STR00002##
[0061] In Chemical Formula 1,
[0062] each of R1, R2 and R3 is independently H, OH or a
C.sub.1-C.sub.10 alkoxy group, with one of R1, R2 and R3 being OH,
and
[0063] each of x and y is independently an integer of 1-2.
[0064] The crosslinking agent compound may be prepared by reacting
a compound represented by Chemical Formula 2 with a compound
represented by Chemical Formula 3.
##STR00003##
[0065] In Chemical Formula 2,
[0066] each of x and y is independently an integer of 1-2.
##STR00004##
[0067] In Chemical Formula 3,
[0068] each of R1, R2 and R3 is independently H, OH or a
C.sub.1-C.sub.10 alkoxy group, which may be the same or different
from each other.
[0069] The crosslinking agent compound may be a compound
represented by Chemical Formula 4.
##STR00005##
[0070] In Chemical Formula 4,
[0071] each of x and y is independently an integer of 1-2.
[0072] In the present disclosure, the isocyanate-based crosslinking
agent and the crosslinking agent of Chemical Formula 1 may be used
at a ratio of 1:0.1-10 parts by weight, specifically 1:0.5-5 parts
by weight, most specifically 1:0.8-3 parts by weight.
[0073] In the present disclosure, the content of the crosslinking
agent may be adjusted for control of the degree of crosslinking.
The crosslinking agent may be used in an amount of 0.1-20 parts by
weight, specifically 0.5-15 parts by weight, more specifically 1-10
parts by weight, more specifically 1-5 parts by weight, based on
100 parts by weight of the thermoplastic polyurethane resin. When
the crosslinking agent compound is used in a smaller amount,
crosslinking may not occur sufficiently. And, if the crosslinking
agent compound is used in a larger amount, it is difficult to
achieve good injection moldability at 150.degree. C. or above
because the degree of crosslinking becomes 99% or higher.
[0074] The crosslinked polyurethane may have a degree of
crosslinking of 10-90.
[0075] Due to the crosslinked structure, the crosslinked
polyurethane may have improved scuff resistance owing to enhanced
physical properties such as tensile strength, tear strength, etc.
and may have very improved light resistance.
[0076] In particular, the crosslinked polyurethane may experience
color change (.DELTA.E) of 8 or less after exposure to irradiance
of 1 SUN (1,000 W/m.sup.2) for 120 hours.
[0077] The outer cover of a golf ball of the present disclosure may
further contain a commonly used additive. The additive may be, for
example, a thermoplastic polymer excluding thermoplastic
polyurethane (TPU), a pigment with desired color, an antioxidant, a
UV absorbent, an organic or inorganic filler, etc., although not
being specially limited thereto. The thermoplastic polymer may be
selected adequately for hardness control of the cover, improvement
of resilience, improvement of injection moldability, improvement of
interfacial adhesivity, etc. For example, polyester resin, nylon
resin, ionomer resin, polyethylene, etc. may be used.
[0078] Specifically, the additive may be added in an amount of
0.1-5 parts by weight based on 100 parts by weight of the
thermoplastic polyurethane resin. Although the additive may be
mixed with the thermoplastic polyurethane and the crosslinking
agent before the extrusion reaction, it may be added after the
crosslinking process is finished if it can affect the reaction.
[0079] For preparation of the crosslinked polyurethane, the
extrusion reaction may be performed in an extruder equipped with a
feeder, a cooling bath and a pelletizer. Specifically, the
extrusion reaction may be performed with the barrel temperature
maintained at 150.degree. C. so that crosslinking can occur
sufficiently. The barrel temperature may be maintained more
specifically at 150-230.degree. C., further more specifically at
160-220.degree. C. During the extrusion reaction, the screw
rotation speed may be maintained at 30-300 rpm to ensure sufficient
crosslinking.
[0080] An extruded strand discharged from a nozzle head after the
extrusion reaction is cooled sufficiently as it passes through the
cooling bath. Then, it is prepared into a pellet form by the
pelletizer. Through this process, a crosslinked polyurethane outer
cover composition can be obtained.
[0081] The crosslinked polyurethane golf ball outer cover can be
prepared by injection molding rather than by the previous casting
method.
[0082] After the injection molding, the polyurethane golf ball
outer cover may be annealed at 50-110.degree. C. for about 2-24
hours to further enhance mechanical and thermal properties.
[0083] The golf ball of the present disclosure includes a core,
which has a single-core, dual-core or triple-core structure.
[0084] Specifically, cured polybutadiene (PBR) rubber may be used
as the core. The cured rubber may be prepared by thermal forming of
rubber stock at a temperature of 150-170.degree. C. under a
pressure of 150-200 ton. The cured rubber may be formed from the
PBR as well as ZDA (zinc diarcylate), zinc oxide, a peroxide
initiator, an oxidation stabilizer, etc.
[0085] The golf ball may further include an inner cover between the
core and the outer cover, and the inner cover may contain an
ionomer resin, which is a copolymer of ethylene and unsaturated
carboxylic acid with a part of the unsaturated carboxylic acid
being neutralized with a monovalent or divalent metal ion. The
ionomer resin may be SURLYN.RTM.. Specifically, SURLYN.RTM.
HPF1000, HPF2000, HPF AD1035, HPF AD1040, SURLYN.RTM. 6120, 7930,
7940, 8320, 8940, 9910, 9970, etc. may be used either alone or in
combination.
[0086] The inner cover may be formed by injection molding on the
surface of the golf ball core.
[0087] Accordingly, the golf ball of the present disclosure may be
a three-piece, four-piece or five-piece golf ball depending on the
core constituting the golf ball and the number of layers of the
cover, although not being limited thereto.
[0088] The golf ball of the present disclosure exhibits excellent
driving distance and spin performance and has greatly improved
scuff resistance and light resistance.
[0089] Hereinafter, the present disclosure is described in more
detail through examples and test examples. However, the examples
according to the present disclosure may be changed into various
different forms and it should not be interpreted that the scope of
the present disclosure is limited by the examples described below.
The examples of the present disclosure are provided to more fully
describe the present disclosure to those having ordinary knowledge
in the art.
Preparation Example 1: Preparation of Novel Crosslinking Agent
Compound
[0090] 228 g (1.5 mol) of vanillin represented by Chemical Formula
5 was added to a 1-L round-bottom flask and melted while
maintaining temperature at 80.degree. C.
##STR00006##
[0091] Then, after adding 110 g (0.5 mol) of Jeffamine.RTM. T-403,
which is a triamine compound, a crosslinking agent compound was
prepared by conducting reaction for about 5 hours in vacuo while
removing water completely.
[0092] The FT-IR spectra of the prepared crosslinking agent
compound and the reactants vanillin and Jeffamine.RTM. T-403 are
shown respectively in FIGS. 1-3.
[0093] The carbonyl peak (C.dbd.O, 1666 cm.sup.-1) of the aldehyde
group in vanillin is clearly observed in FIG. 2, and the primary
amine peaks (--NH.sub.2 stretching, 3369, 3288 cm.sup.-1, NH
stretching 1591 cm.sup.-1) of Jeffamine.RTM. T-403 are clearly
observed in FIG. 3.
[0094] As seen from FIG. 1, the carbonyl peak and amine peaks
disappeared in the crosslinking agent compound and a new imine peak
(C.dbd.N, 1643 cm.sup.-1) appeared, suggesting that an imine group
was formed by condensation.
[0095] The .sup.1H NMR spectra of the prepared crosslinking agent
compound and the reactants vanillin and Jeffamine.RTM. T-403 are
shown respectively in FIGS. 4-6.
[0096] As seen from FIG. 4, the aldehyde peak .delta. 9.84 (s, 1H)
of vanillin and the amine peaks b 2.2-2.6 (broad, 2H) of
Jeffamine.RTM. T-403 disappeared in the crosslinking agent compound
and a characteristic peak of an imine group appeared at b 8.20 (d,
3H), suggesting that an imine group was formed by condensation.
[0097] <Prepared Crosslinking Agent Compound>
[0098] .sup.1H NMR (400 MHz, acetone-d.sub.6): .delta. 0.77-0.92
(m, 3H), 1.0-1.2 (m, 9H), 1.20-1.50 (m, 9H), 2.90 (b, 2H), 3.1-3.8
(m, 18H), 3.85 (m, 9H), 6.85 (d, 3H), 7.18 (t, 3H), 7.45 (s, 3H),
8.20 (d, 3H).
[0099] <Vanillin>
[0100] .sup.1H NMR (400 MHz, acetone-d.sub.6): .delta. 3.95 (s,
3H), 7.02 (d, 1H), 7.47 (m, 2H), 8.72 (s, 1H), 9.84 (s, 1H).
[0101] <Jeffamine.RTM. T-403>
[0102] .sup.1H NMR (400 MHz, acetone-d.sub.6): .delta. 0.77-0.92
(m, 3H), 1.0-1.2 (m, 9H), 1.20-1.50 (m, 9H), 2.90 (b, 2H), 3.1-3.8
(m, 18H), 3.85 (m, 9H), 6.85 (d, 3H), 7.18 (t, 3H), 7.45 (s, 3H),
8.20 (d, 3H).
Examples 1-4 and Comparative Example 1-3: Preparation of
Crosslinked Polyurethane
Examples 1-4
[0103] A crosslinking agent composition was obtained by mixing the
alicyclic polyisocyanurate t-IPDI (Vestanat T1890, Evonik) and the
compound prepared in Preparation Example 1 at a weight ratio of
1:1.
[0104] Then, 1, 3, 5 or 10 parts by weight of the crosslinking
agent composition was dry-mixed with 100 parts by weight of
thermoplastic polyurethane (Elastollan NY95A, non-yellowing type,
BASF) under nitrogen atmosphere as described in Table 1.
[0105] The mixture was extruded using a twin-screw extruder with
L/D=40 under the condition of feeder speed 3.0 rpm, screw speed 110
rpm and barrel temperature 160-220.degree. C.
[0106] The extrusion product was cooled by passing through a
cooling bath and then the crosslinked polyurethane was prepared
into pellet shape by passing through a pelletizer.
Comparative Example 1
[0107] A pellet was prepared in the same manner as in the examples
except that a crosslinking agent was not used.
Comparative Example 2
[0108] A pellet was prepared in the same manner as in the examples
except that 3 parts by weight of aromatic isocyanate MDI (methylene
diphenyl diisocyanate) was mixed with 100 parts by weight of
thermoplastic polyurethane.
Comparative Example 3
[0109] A pellet was prepared in the same manner as in the examples
except that 3 parts by weight of polyisocyanurate t-IPDI (Vestanat
T1890, Evonik) was mixed as a crosslinking agent with 100 parts by
weight of thermoplastic polyurethane (Elastollan 1195A, BASF),
which is yellowing type aromatic thermoplastic polyurethane.
[0110] Measurement of Degree of Crosslinking
[0111] The gel content of the crosslinked polyurethane obtained in
Examples 1-4 and Comparative Examples 1-3 was measured to
investigate the degree of crosslinking. After adding about 1.5 g of
the pellet-shaped crosslinked polyurethane to 50 mL of DMF
(dimethylformamide) and stirring at 25.+-.3.degree. C. for 24
hours, crosslinked urethane in the form of swollen gel without
being dissolved was filtered through glass fiber filter (GF/A .phi.
47 mm) under reduced pressure. Then, gel content (wt %) was
measured by weighing in an oven at 110.degree. C. The result is
shown in Table 1.
[0112] As seen from Table 1, it was confirmed that crosslinked
polyurethane was formed by extrusion of thermoplastic polyurethane
using a crosslinking agent in Examples 1-4 and Comparative Examples
2-3. In particular, it can be seen that the degree of crosslinking
(gel content, wt %) was increased as the content of the
crosslinking agent was increased from 1 to 10 parts by weight in
Examples 1-4.
[0113] However, Example 2 and Comparative Example 3 showed
significant difference in gel content as 56 wt % and 20 wt %
although the content of the crosslinking agent was the same at 3
parts by weight.
[0114] It is thought that this significant difference is caused by
the chemical structure of the hard segment of TPU used for
preparation of the crosslinked polyurethane. Whereas non-yellowing
type aliphatic TPU (aliphatic TPU) was used in Example 2, aromatic
TPU was used in Comparative Example 3. It is thought that the
reason why crosslinking was not achieved sufficiently at the same
crosslinking agent content when aromatic TPU was used in
Comparative Example 3 is because of the very strong assembly of
hard segments owing to the .pi.-.pi. stacking of aromatic benzene
rings constituting the hard segments, leading to relatively
difficult reaction with the crosslinking agent even at the
extrusion reaction temperature of 200.degree. C. or higher.
[0115] Accordingly, for preparation of injection-molded crosslinked
polyurethane for a golf ball cover, it is preferred to use
non-yellowing type aliphatic TPU, which allows easier opening of
the hard segment, rather than aromatic TPU.
[0116] Meanwhile, the result of measuring the gel content of
Examples 1-4, it can be seen that injection molding is difficult if
the crosslinking agent is 10 parts by weight or higher because the
degree of crosslinking becomes 90 or higher, and that significant
improvement in tear strength, scuff resistance, etc. cannot be
expected if the degree of crosslinking becomes 20 or lower.
[0117] For Comparative Example 1, the gel content was 0 because TPU
was not crosslinked but was completely dissolved in DMF.
[0118] Measurement of Light Resistance
[0119] The crosslinked polyurethane obtained in Examples 1-4 and
Comparative Examples 2-3 and the polyurethane of Comparative
Example 1 was subjected to light resistance testing.
[0120] First, after preparing a test sample with a size of 20
mm.times.20 mm.times.2 mm by injection molding, color change
(.DELTA.E) upon exposure to light was measured. The result is shown
in Table 1.
[0121] The temperature-controllable chamber LT400-50HP (TNE Tech)
was used for the light resistance testing, and BYK's Spectro guide
model was used as a colorimeter.
[0122] The light resistance testing was conducted by exposing to
artificial solar light with an irradiance of 1 SUN (1,000
W/m.sup.2) for 120 hours at a chamber temperature of 25.degree. C.
After the light exposure, the color change (.DELTA.E) of the sample
before and after the testing was measured with the colorimeter. The
color change is defined by
.DELTA.E=[(.DELTA.L).sup.2+(.DELTA.a).sup.2+(.DELTA.b).sup.2].sup.1/2,
or the square root of the sum of the squares of the change in color
lightness (L) and hues (a, b). It reflects the overall change in
color.
[0123] As a result of measuring the color change of the crosslinked
polyurethane obtained in Examples 1-4 of the present disclosure,
the color change was hardly distinguishable visually with .DELTA.E
less than 2, as shown in Table 1. In contrast, Comparative Examples
2-3 showed visually distinguishable color change with .DELTA.E of
8.5 and 11.6, respectively.
[0124] Accordingly, it can be seen that the crosslinked
polyurethane obtained by crosslinking aliphatic TPU with
non-aromatic isocyanate as in Examples 1-4 can be used for a cover
of a colored golf ball.
[0125] Measurement of Strength
[0126] The mechanical properties of the crosslinked polyurethane
obtained in Examples 1-4 and Comparative Examples 2-3, such as
hardness (Shore D), tensile strength, tear strength, etc., were
tested.
[0127] A test sample was prepared by injection molding and hardness
was measured according to ASTM D2240 using a Shore D hardness
tester (Zwick, Germany). Tensile strength and tear strength were
measured according to ASTM D412 and ASTM D 624, respectively, using
Cometech's UTM (QC-506M2). The results are shown in Table 1.
[0128] It was confirmed that the crosslinked polyurethane of
Examples 1-4 showed increased hardness, tensile strength and tear
strength as compared to the uncrosslinked polyurethane of
Comparative Example 1.
TABLE-US-00001 TABLE 1 Example Comparative Example 1 2 3 4 1 2 3
Composition TPU (parts 100 100 100 100 100 100 100 of by weight)
(aromatic) crosslinked Crosslinking 1 3 5 10 0 3 3 urethane agent
(parts by (aromatic) weight) Degree of crosslinking (gel 30 56 80
95 0 64 20 content, wt %) Light resistance (.DELTA.E) 0.74 0.93
0.86 1.10 0.90 8.5 11.6 Strength hardness 43 45 47 48 43 45 40
(Shore D) Tensile strength 40 44 47 53 38 48 42 (MPa) Tear strength
8.2 9.1 10.5 11.0 5.3 9.0 7.8 (kgf/mm)
Examples 5-8 and Comparative Examples 4-7: Preparation of Cover
Composition
Examples 5-8
[0129] 100 parts by weight of the crosslinked polyurethane prepared
in Example 2 or 3 was mixed with a pigment (white, yellow, orange
or green color) at a content described in Table 2.
[0130] The mixture was extruded using an extruder with L/D=40 under
the condition of feeder speed 3.0 rpm, screw speed 120 rpm and
barrel temperature 170-190.degree. C. After cooling, a crosslinked
polyurethane cover composition was prepared by passing through a
pelletizer.
Comparative Examples 4-5
[0131] A polyurethane cover composition was prepared in the same
manner as in Examples 5-8 except that the thermoplastic
polyurethane of Comparative Example 1 was mixed with 2 parts by
weight of a white pigment and 0.3 part by weight of a yellow
pigment as described in Table 2.
Comparative Examples 6-7
[0132] A polyurethane cover composition was prepared in the same
manner as in Examples 5-8 except that the crosslinked polyurethane
prepared in Comparative Example 2 or 3 was mixed with 0.3 parts by
weight of a yellow pigment and an orange pigment, respectively, as
described in Table 2.
[0133] In order to investigate the light resistance of the cover
compositions obtained in Examples 5-8 and Comparative Examples 4-7,
color change was measured as described above. The results are shown
in Table 2.
TABLE-US-00002 TABLE 2 Example Comparative Example 5 6 7 8 4 5 6 7
Cover Crosslinked urethane 100 100 100 -- -- -- composition
(Example 2) Crosslinked urethane -- -- -- 100 -- -- (Example 3)
thermoplastic 100 100 Polyurethane (Comparative Example 1)
Crosslinked urethane 100 (Comparative Example 2) Crosslinked
urethane 100 (Comparative Example 3) Pigment, white 2 2 Pigment,
yellow 0.3 0.3 0.3 Pigment, orange 0.3 0.3 Pigment, green 0.3 Light
resistance (.DELTA.E) 0.52 1.20 1.05 0.83 0.74 0.69 10.70 12.0
[0134] As seen from Table 2, the color change for the cover
compositions of Examples 5-8 was almost visually undistinguishable
with .DELTA.E of 0.83-1.20, confirming that they have excellent
light resistance.
[0135] However, the cover compositions of Comparative Examples 6-7
had the color change .DELTA.E values of 10.7-12.0, significantly
different from those of Examples 5-8, indicating that they have
light resistance problems.
[0136] Preparation of Golf Ball
[0137] Golf balls were prepared using the cover composition of
Examples 5-8 and Comparative Examples 4-5. Three-piece (one
core+two covers) golf balls were prepared by forming the
polyurethane outer cover on the core and the inner cover. The
driving distance, spin and scuff resistance of the golf balls were
tested. The results are shown in Table 3.
[0138] As the golf ball core, a single core with a diameter 38.70
mm prepared from cured polybutadiene rubber was used. As the inner
cover, ionomer resin (Surlyn.RTM. 8940 and 9910 blended at a weight
ratio of 50/50) was injection-molded on the single core to a
thickness 1.00, 1.20 or 1.50 mm.
[0139] The polyurethane outer cover was formed by injection-molding
on the surface of the inner cover. The thickness of the outer cover
was set to 0.5, 0.8 or 1.0 mm. The outer cover was molded using the
Insert 100, vertical-type injection molding machine (Engel,
Germany). A hot runner mold was used, and a cavity with 332 dimples
was used.
[0140] The total thickness of the golf ball cover prepared in this
example was 2.00 mm, including the outer urethane layer and the
inner ionomer layer.
[0141] The three-piece golf ball prepared in this example had a
weight of 45.50-45.70 g and a diameter of 42.70-42.75 mm. The
results of measuring the driving distance, spin and scuff
resistance of each golf ball are shown in Table 3.
[0142] It can be seen that the driving distance of the golf ball
prepared from the cover composition of the examples of the present
disclosure decreases gradually as the thickness of the polyurethane
outer cover is increased. This is due to the soft material property
of urethane.
[0143] Accordingly, in order to increase the driving distance of
the golf ball, it is preferred to decrease the thickness of the
urethane cover. However, when the thickness is decreased, although
the driving distance is increased, the cover may be damaged when
the golf ball is hit by a driver, an iron or a wedge due to poor
scuff resistance.
[0144] It was confirmed that scuff resistance was excellent when
the crosslinked polyurethane of Examples 5-8 was used as compared
to when the polyurethane of Comparative Examples 4-5 was used.
[0145] In particular, the golf ball of Example 5 was excellent not
only in driving distance and spin but also in scuff resistance even
when the thickness of the outer cover was decreased to 0.5 mm. This
confirms that the thickness of the cover prepared from the
crosslinked polyurethane of the present disclosure can be decreased
to about 0.5 mm.
[0146] Accordingly, the cover thickness of the polyurethane golf
ball using the crosslinked polyurethane of the present disclosure
can be determined to be specifically 1.0 mm or smaller, more
specifically to 0.4-0.8 mm, in consideration of driving
distance.
TABLE-US-00003 TABLE 3 Comparative Golf ball Example Example
characteristics 5 6 7 8 4 5 Cover color White Yellow Orange Green
White Yellow Cover hardness 45 46 45 47 43 45 Outer cover 0.50 0.80
1.00 1.00 0.80 1.00 thickness Inner cover 1.50 1.20 1.00 1.00 1.20
1.00 thickness Core size 38.7 38.7 Driving 240 238 234 235 237 235
distance (m) Spin (rpm) 9445 9479 9505 9946 9430 9440 Scuff
resistance .circleincircle. .circleincircle. .circleincircle.
X~.DELTA. X~.DELTA.
[0147] The golf ball characteristics described in Table 3 were
measured as follows.
[0148] Driving distance (m): The mechanical golfer Iron Byron (True
Temper Sports, USA) was used. The sum of carry distance and run
distance when the golf ball was hit by a titanium driver with a
loft angle of 10.5.degree. and a head speed of 44.7 m/sec (100 mph)
was measured.
[0149] Spin (RPM): The spin (revolutions per minute) was measured
with Trackman when the golf ball was hit by the same mechanical
golfer as in the driving distance measurement with a wedge angle of
52.degree. and a head speed of 31 m/sec.
[0150] Scuff resistance: After keeping the golf ball at 23.degree.
C. and hitting it with a swing robot and a pitching wedge with a
head speed of 33 m/s, the state of the golf ball surface was
evaluated as follows.
[0151] .circleincircle.: No or hardly visible surface scratch.
[0152] .largecircle.: Slight surface scratch little concern.
[0153] .DELTA.: Slightly fluffy surface.
[0154] X: Cut or broken surface.
[0155] Although the inventions are shown in the exemplary
embodiments, those skilled in the art will appreciate that many
variations and modifications can be made to the embodiments without
substantially departing from the principles of the present
inventive concept. Therefore, the disclosed embodiments of the
invention are used in a generic and descriptive sense only and not
for purposes of limitation. The scope of protection of the present
inventive concept should be interpreted by the following claims,
and all technical ideas within the scope equivalent thereto should
be construed as being included in the scope of the technical idea
defined by the present disclosure.
* * * * *